TUBE STOCK OUT OF MEDIUM CARBON LOW ALLOYED STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: tube stock with diameter from 80 to 180 mm produced out of steel containing wt %: carbon 0.41-0.48, manganese 0.90-1.15, silicon 0.17-0.37, nitrogen 0.005-0.015, arsenic 0.0001-0.03, tin 0.0001-0.02, lead 0.0001-0.01, zinc 0.0001-0.005, iron and unavoidable impurities - the rest at following ratio: As+Sn+Pb+5×Zn≤0.07; C+Mn/6≤0.65. Impurities are: chromium not more, than 0.30%, nickel not more, than 0.30%, molybdenum not more, than 0.10%, vanadium not more, than 0.02%, titanium not more than 0.02%, sulphur not more than 0.030%, calcium not more than 0.01%, niobium not more than 0.02%, phosphorus not more than 0.035%, copper not more than 0.30%. Tube stock is continuous cast, hot rolled, normalized, it has ferrite-pearlite structure, dimension of actual grain is 6-9 points, its macrostructure for central porosity, pointed non-uniformity, liquation square, sub-shrinking liquation, liquation strips - not more than 3 points in each kind, non-metallic inclusions - sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates - not more, than 4.5 points for each kind of inclusions.Stock possesses tensile strength of 638 H/mm², yield strength not less than 373 H/mm², contraction ratio not less than 40%, impact resilience KCU+20°C not less than 39 J/cm².

EFFECT: upgraded level of consumer characteristics.

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